The role of diet on the rhythm of physiological responses of lactating ewes under heat stress

ABSTRACT

The aim of this study was to evaluate the role of diet on the rhythm of physiological responses of lactating ewes under heat stress. Twenty-four hair ewes, twelve Santa Inês (SI) and twelve Morada Nova (MN) were used. The data were analyzed using a factorial arrangement in a completely randomized design with two periods, two treatments and two breeds. Physiological responses and thermal variables were obtained at weekly interval, during eight weeks of lactation. Severe (morning) and extremely severe (afternoon) heat stress were observed. Results showed a high correlation between physiological responses with thermal variables. The interaction among breed x supplementation level x week of lactation had effect (P < 0.05) on plasma cortisol, with higher levels in SI (0.5 and 1.5 % BW) and MN ewes subjected to 1.5 % compared to MN ewes subjected to 0.5 % concentrate supplementation. An effect (P < 0.001) of interaction between breed x period of the day were seen on respiratory rate with higher values in the afternoon and SI ewes that received 1.5 % of concentrate supplementation. Heat stress and level of concentrate supplementation, in semiarid environment, promoted changes in physiological responses of lactating ewes.

KEYWORDS:

• Adaptation
• climatic conditions
• nutrition
• hair breed

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research received no specific grant from any funding agency in the public, commercial, or notfor-profit sectors.